Yes qemu had too much cases in the past where it came to data corruption for
using the disk multiple times.
That has caused quite some pain (as you found in the old bugs) but turned out
to be much more reliable.
The different entry points use different options to eventually achieve the same
which is to explicitly allow sharing the disks as needed in the rare cases that
this applies:
1. manual qemu usage: cmdline needs to set share-rw=on
2. usage through libvirt: sets share-rw=on if "<sharable>" is set, see bug
1716028 and refs from there)
3. tools like qemu-img: need to set --force-share as you already identified
4. openstack: well this used #2 (and has to set sharable as needed and #3 which
is fixed (by bug 1718295 and bug 1718133 that you already found)
That should be in all of the virt-stack that is on Bionic and later
(where the qemu with the change is) and in the related Cloud Archive
versions.
The TL;DR is:
- images really shared (like an ISO) need to marked sharable
- things not really meant to be opened multiple times e.g. same root disk file
(that only worked by chance before) should not be used that way
I don't see in the comments above what would be left, are there charms
using qemu-img that need to be adapted (that might be what comment #6
says) or what exactly is the missing bit here?
For qemu/libvirt all that I know to be needed for this is fixed released
- setting accordingly unless we identify something new that we will
need.
** Also affects: libvirt (Ubuntu)
Importance: Undecided
Status: New
** Changed in: libvirt (Ubuntu)
Status: New => Fix Released
** Changed in: qemu (Ubuntu)
Status: New => Fix Released
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https://bugs.launchpad.net/bugs/1816170
Title:
KVM instances fail at creation with: Failed to get shared "write" lock
Is another process using the image?
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